Remove spl-dkms conflict with spl-kmod

Because the spl-dkms package also provides spl-kmod for the
spl user package yum flags this as a conflict.  To avoid the
problem remove the Conflicts tag from spl-dkms and just rely
on the one in spl-kmod.

  spl-dkms-0.6.0-rc14.fc18.noarch has installed conflicts
    spl-kmod: spl-dkms-0.6.0-rc14.fc18.noarch

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Use requested kernel for dkms builds

The --with-linux and --with-linux-obj options must be specified
as part of the dkms build otherwise the package will be built
against the running kernel.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>